class Example01 {
	public static void main (String[] args){
		Student stu1 = new Student ();
		Student stu2 = new Student ();
		stu1.name = "小明";
		stu1.red ();
		stu1.name = "小华";
		stu2.red ();
	}
}

// 3-2
class Student {
	String name;
	void read () {
		System.out.println("大家好，我是"name+",年龄"+age);
	}
}
class Example02 {
	public static void main (String[] args){
		Student stu1 = new Student ();
		Student stu2 = null;
		stu2 = stu1
		stu1.name = "小明";
		stu1.age = 20 ;
		stu2.age = 50;
		stu1.red ();
		stu2.red ();
		
	}
}


class student {
	 String name;
	 int age;
	 void read () {
		 System.out.println("大家好，我是"name+",年龄"+age);
	 }
 }
  public class Example03 {
 	public static void main (String[] args){
 		Student stu = new Student ();
 		stu1.name = "张三";
 		stu.age = -18;
 		stu.read () ;
 	}
 }